The broad long-term objective of this project is to afford a better means of assessing the transepidermal water loss (TEWL) from the skin of premature infants. Such an assessment is essential if fluid management efforts are to be successful. The specific aim is to develop and conduct clinical trials on a cribside computer-based monitoring system to determine the cumulative TEWL experienced by an infant. The experimental design is centered around a personal computer which receives and processes environmental data relevant to the infant being nursed in a neonatal intensive care unit. Pertinent environmental data include the relative humidity and temperature of the air near the infant and the radiant heat received by the infant. Since the skin of a premature infant matures quite rapidly during the first two weeks of life, baseline measurements of the TEWL will be obtained once a day using a method developed by the principal investigator. Using this baseline data and the continuous environmental data, the cribside computer will then determine instantaneous and cumulative TEWL over the subsequent 24-hour period. The cumulative TEWL determined in this manner will be compared to that determined through weight change measurements performed once a day, taking into account known fluid intake and output totals over the same period of time. These investigations will be conducted over two-week periods on ten (10) premature infants with birthweights less than 1500 gm and initial postnatal ages less than 5 days.